1. Field of the Invention
The present invention relates to a projection-type image display apparatus.
2. Description of the Related Art
Generally, in a projection-type image display apparatus, a periphery of a screen on which an image is projected is supported by a frame. Because the frame faces towards viewers, an excellent design is needed for the frame. Furthermore, to facilitate excellent design and reduction in size of the projection-type image display apparatus, a design bezel, which serves as a front-surface frame portion of the frame, needs to be as narrow as possible.
In response to the needs mentioned earlier, various technologies have been proposed. According to a transmissive screen device disclosed in Japanese Patent Application Laid-open No. 2007-248763, an upper side of a screen is fixedly held to an upper fixing frame and the screen is suspended along and in contact with both surfaces of a reinforcing board. Moreover, on a lower side of the screen, a downward tension due to a leaf spring is uniformly applied in a width direction. Additionally, a lower frame supports a lower side of the reinforcing board and bears a weight of the screen and the reinforcing board and the tension due to the leaf spring.
According to the technology disclosed in Japanese Patent Application Laid-open No. 2007-248763, because the screen is suspended along both surfaces of the reinforcing board, without being restricted by the reinforcing board, the screen can be expanded and contracted such that the screen can slide over the surfaces of the reinforcing board. Moreover, in addition to a weight of a laminated body, a supporting unit also bears the tension applied to the screen via a holding unit. Thus, the frame can be reduced in size without excessively increasing rigidity of an upper portion of the frame.
A screen holding device disclosed in Japanese Patent No. 3225753 includes a screen frame, a block piece that is fixed to each side of the screen frame and that includes a U-shaped cross section and an L-shaped cross section alternating with each other, and a screen pushing member that includes, at a position corresponding to the U-shaped section of the block piece, a nearly V-shaped projection of a predetermined height. The projection of the screen pushing member is elastically brought into contact with and inserted into the U-shaped section of the block piece and the screen is fixed to the screen frame. According to the technology disclosed in Japanese Patent No. 3225753, the screen can be easily held without using screws, and performance in assembly and replacement can be enhanced at a low cost.
However, according to the above technologies, the frame that forms the holding unit or the screen frame is fabricated by plastic injection molding. However, when the frame is fabricated by aluminum extrusion, etc. and not by the injection molding, for example, an L-shaped coupling member is required at a corner at which a top side frame and a lateral side frame abut each other. The coupling member does not intervene with the screen and a width dimension of the design bezel increases. In other words, in the above technologies, because the coupling member is arranged on a periphery of the screen on the same surface of the screen, the width dimension of the design bezel increases.